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Liu Y, Elbanna A, Gao W, Pan J, Shen Z, Teng J. Interlayer Excitons in Transition Metal Dichalcogenide Semiconductors for 2D Optoelectronics. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2107138. [PMID: 34700359 DOI: 10.1002/adma.202107138] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/13/2021] [Indexed: 06/13/2023]
Abstract
Optoelectronic materials that allow on-chip integrated light signal emitting, routing, modulation, and detection are crucial for the development of high-speed and high-throughput optical communication and computing technologies. Interlayer excitons in 2D van der Waals heterostructures, where electrons and holes are bounded by Coulomb interaction but spatially localized in different 2D layers, have recently attracted intense attention for their enticing properties and huge potential in device applications. Here, a general view of these 2D-confined hydrogen-like bosonic particles and the state-of-the-art developments with respect to the frontier concepts and prototypes is presented. Staggered type-II band alignment enables expansion of the interlayer direct bandgap from the intrinsic visible in monolayers up to the near- or even mid-infrared spectrum. Owing to large exciton binding energy, together with ultralong lifetime, room-temperature exciton devices and observation of quantum behaviors are demonstrated. With the rapid advances, it can be anticipated that future studies of interlayer excitons will not only allow the construction of all-exciton information processing circuits but will also continue to enrich the panoply of ideas on quantum phenomena.
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Affiliation(s)
- Yuanda Liu
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Ahmed Elbanna
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
| | - Weibo Gao
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jisheng Pan
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
| | - Zexiang Shen
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 637371, Singapore
- The Photonics Institute and Center for Disruptive Photonic Technologies, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore
| | - Jinghua Teng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Singapore, 138634, Singapore
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Combescot M, Combescot R, Dubin F. Bose-Einstein condensation and indirect excitons: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:066501. [PMID: 28355164 DOI: 10.1088/1361-6633/aa50e3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We review recent progress on Bose-Einstein condensation (BEC) of semiconductor excitons. The first part deals with theory, the second part with experiments. This Review is written at a time where the problem of exciton Bose-Einstein condensation has just been revived by the understanding that the exciton condensate must be dark because the exciton ground state is not coupled to light. Here, we theoretically discuss this missed understanding before providing its experimental support through experiments that scrutinize indirect excitons made of spatially separated electrons and holes. The theoretical part first discusses condensation of elementary bosons. In particular, the necessary inhibition of condensate fragmentation by exchange interaction is stressed, before extending the discussion to interacting bosons with spin degrees of freedom. The theoretical part then considers composite bosons made of two fermions like semiconductor excitons. The spin structure of the excitons is detailed, with emphasis on the crucial fact that ground-state excitons are dark: indeed, this imposes the exciton Bose-Einstein condensate to be not coupled to light in the dilute regime. Condensate fragmentations are then reconsidered. In particular, it is shown that while at low density, the exciton condensate is fully dark, it acquires a bright component, coherent with the dark one, beyond a density threshold: in this regime, the exciton condensate is 'gray'. The experimental part first discusses optical creation of indirect excitons in quantum wells, and the detection of their photoluminescence. Exciton thermalisation is also addressed, as well as available approaches to estimate the exciton density. We then switch to specific experiments where indirect excitons form a macroscopic fragmented ring. We show that such ring provides efficient electrostatic trapping in the region of the fragments where an essentially-dark exciton Bose-Einstein condensate is formed at sub-Kelvin bath temperatures. The macroscopic spatial coherence of the photoluminescence observed in this essentially dark region confirms this conclusion.
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Affiliation(s)
- Monique Combescot
- Institut des NanoSciences de Paris, Université Pierre et Marie Curie, CNRS, Tour 22, 4 place Jussieu, 75005 Paris, France
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Schneider C, Winkler K, Fraser MD, Kamp M, Yamamoto Y, Ostrovskaya EA, Höfling S. Exciton-polariton trapping and potential landscape engineering. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:016503. [PMID: 27841166 DOI: 10.1088/0034-4885/80/1/016503] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Exciton-polaritons in semiconductor microcavities have become a model system for the studies of dynamical Bose-Einstein condensation, macroscopic coherence, many-body effects, nonclassical states of light and matter, and possibly quantum phase transitions in a solid state. These low-mass bosonic quasiparticles can condense at comparatively high temperatures up to 300 K, and preserve the fundamental properties of the condensate, such as coherence in space and time domain, even when they are out of equilibrium with the environment. Although the presence of a confining potential is not strictly necessary in order to observe Bose-Einstein condensation, engineering of the polariton confinement is a key to controlling, shaping, and directing the flow of polaritons. Prototype polariton-based optoelectronic devices rely on ultrafast photon-like velocities and strong nonlinearities exhibited by polaritons, as well as on their tailored confinement. Nanotechnology provides several pathways to achieving polariton confinement, and the specific features and advantages of different methods are discussed in this review. Being hybrid exciton-photon quasiparticles, polaritons can be trapped via their excitonic as well as photonic component, which leads to a wide choice of highly complementary trapping techniques. Here, we highlight the almost free choice of the confinement strengths and trapping geometries that provide powerful means for control and manipulation of the polariton systems both in the semi-classical and quantum regimes. Furthermore, the possibilities to observe effects of the polariton blockade, Mott insulator physics, and population of higher-order energy bands in sophisticated lattice potentials are discussed. Observation of such effects could lead to realization of novel polaritonic non-classical light sources and quantum simulators.
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Affiliation(s)
- C Schneider
- Technische Physik, Physikalisches Institut and Wilhelm-Conrad-Röntgen-Research Center for Complex Material Systems, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany
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Sivalertporn K, Muljarov EA. Controlled Strong Coupling and Absence of Dark Polaritons in Microcavities with Double Quantum Wells. PHYSICAL REVIEW LETTERS 2015; 115:077401. [PMID: 26317745 DOI: 10.1103/physrevlett.115.077401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Indexed: 06/04/2023]
Abstract
We demonstrate an efficient switching between strong and weak exciton-photon coupling regimes in microcavity-embedded asymmetric double quantum wells, controlled by an applied electric field. We show that a fine-tuning of the electric field leads to drastic changes in the polariton properties, with the polariton ground state being redshifted by a few meV and having acquired prominent features of a spatially indirect dipolar exciton. We study the properties of dipolar exciton polaritons, called dipolaritons, on a microscopic level and show that, unlike recent findings, they are not dark polaritons but, owing to the finite size of the exciton, are mixed states with a comparable contribution of the cavity photon, bright direct, and long-living indirect exciton modes.
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Affiliation(s)
- K Sivalertporn
- Department of Physics, Faculty of Science, Ubon Ratchathani University, Ubon Ratchathani 34190, Thailand
| | - E A Muljarov
- School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
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Berman OL, Kezerashvili RY, Kolmakov GV, Pomirchi LM. Spontaneous formation and nonequilibrium dynamics of a soliton-shaped Bose-Einstein condensate in a trap. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:062901. [PMID: 26172766 DOI: 10.1103/physreve.91.062901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Indexed: 06/04/2023]
Abstract
The Bose-stimulated self-organization of a quasi-two-dimensional nonequilibrium Bose-Einstein condensate in an in-plane potential is proposed. We obtained the solution of the nonlinear, driven-dissipative Gross-Pitaevskii equation for a Bose-Einstein condensate trapped in an external asymmetric parabolic potential within the method of the spectral expansion. We found that, in sharp contrast to previous observations, the condensate can spontaneously acquire a solitonlike shape for spatially homogeneous pumping. This condensate soliton performs oscillatory motion in a parabolic trap and, also, can spontaneously rotate. Stability of the condensate soliton in the spatially asymmetric trap is analyzed. In addition to the nonlinear dynamics of nonequilibrium Bose-Einstein condensates of ultracold atoms, our findings can be applied to the condensates of quantum well excitons and cavity polaritons in semiconductor heterostructure, and to the condensates of photons.
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Affiliation(s)
- Oleg L Berman
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - Roman Ya Kezerashvili
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - German V Kolmakov
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
| | - Leonid M Pomirchi
- Physics Department, New York City College of Technology, The City University of New York, Brooklyn, New York 11201, USA
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Xu TF, Jing XL, Luo HG, Wu WC, Liu CS. Interplay between periodicity and nonlinearity of indirect excitons in coupled quantum wells. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:455301. [PMID: 23072970 DOI: 10.1088/0953-8984/24/45/455301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Inspired by a recent experiment of localization-delocalization transition (LDT) of indirect excitons in lateral electrostatic lattices (Remeika et al 2009 Phys. Rev. Lett. 102 186803), we theoretically investigate the interplay between periodic potential and nonlinear interactions of indirect excitons in coupled quantum wells. It is shown that the model involving both attractive two-body and repulsive three-body interactions can lead to a natural account for the LDT of excitons across the lattice when reducing lattice amplitude or increasing particle density. In addition, the observations that the smooth component of the photoluminescent energy increases with increasing exciton density and that the exciton interaction energy is close to the lattice amplitude at the transition are also qualitatively explained. Our model provides an alternative way of understanding the underlying physics of the exciton dynamics in lattice potential wells.
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Affiliation(s)
- T F Xu
- Department of Physics, Yanshan University, Qinhuangdao 066004, People's Republic of China
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7
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Wilkes J, Muljarov EA, Ivanov AL. Drift-diffusion model of the fragmentation of the external ring structure in the photoluminescence pattern emitted by indirect excitons in coupled quantum wells. PHYSICAL REVIEW LETTERS 2012; 109:187402. [PMID: 23215326 DOI: 10.1103/physrevlett.109.187402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Indexed: 06/01/2023]
Abstract
Under optical excitation, coupled quantum wells are known to reveal fascinating features in the photoluminescence pattern originating from dipole orientated indirect excitons. The appearance of an external ring has been attributed to macroscopic charge separation in the quantum well plane. We present a classical model of nonlinear diffusion to account for the observed fragmentation of the external ring into a periodic array of islands. The model incorporates the Coulomb interactions between electrons, holes, and indirect excitons. At low temperatures, these interactions lead to pattern formation similar to the experimentally observed ring fragmentation. The fragmentation is found to persist to temperatures above the quantum degeneracy temperature of indirect excitons.
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Affiliation(s)
- J Wilkes
- Department of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom
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Chernyuk AA, Sugakov VI, Tomylko VV. Exciton phase transitions in semiconductor quantum wells with disc-shaped electrode. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:195803. [PMID: 22517115 DOI: 10.1088/0953-8984/24/19/195803] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Phase transitions in a system of indirect excitons in semiconductor double quantum wells are studied for a set-up when one of the electrodes is of finite size and, in particular, has the shape of a disc. At voltage a region under the rim of the disc is created where excitons have lower energy, thus providing a macroscopic trap attractive for excitons while being repulsive for charged particles. The theory of the formation of patterns of the excitonic condensed phase under the disc is built based on the assumption of the existence of the inter-exciton range where the interaction between them is attractive. The finite value of the exciton lifetime is taken into account serving as a limiting factor for the size of the islands of the condensed phase. The calculations reveal complex restructuring of the patterns of the spatial distribution of exciton density with increasing pumping intensity: from the structureless gaseous phase to separate islands of the condensed phase within the gaseous phase, then to islands of the gaseous phase in the bulk of the condensed phase and finally to the continuous condensed phase.
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Affiliation(s)
- A A Chernyuk
- Institute for Nuclear Research, National Academy of Sciences of Ukraine, Kyiv, Ukraine
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Abstract
The tunneling of electrons through barriers can be controlled when photons are coupled to excited states of electrons trapped in quantum wells.
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10
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Cohen K, Rapaport R, Santos PV. Remote dipolar interactions for objective density calibration and flow control of excitonic fluids. PHYSICAL REVIEW LETTERS 2011; 106:126402. [PMID: 21517333 DOI: 10.1103/physrevlett.106.126402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Indexed: 05/30/2023]
Abstract
In this Letter we suggest a method to observe remote interactions of spatially separated dipolar quantum fluids, and in particular, of dipolar excitons in GaAs bilayer based devices. The method utilizes the static electric dipole moment of trapped dipolar fluids to induce a local potential change on spatially separated test dipoles. We show that such an interaction can be used for model-independent, objective fluid density measurements, an outstanding problem in this field of research, as well as for interfluid exciton flow control and trapping. For a demonstration of the effects on realistic devices, we use a full two-dimensional hydrodynamical model.
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Affiliation(s)
- Kobi Cohen
- Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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11
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Berman OL, Kezerashvili RY, Lozovik YE, Snoke DW. Bose-Einstein condensation and superfluidity of trapped polaritons in graphene and quantum wells embedded in a microcavity. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2010; 368:5459-5482. [PMID: 21041225 DOI: 10.1098/rsta.2010.0208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The theory for spontaneous coherence of short-lived quasiparticles in two-dimensional excitonic systems is reviewed, in particular, quantum wells (QWs) and graphene layers (GLs) embedded in microcavities. Experiments with polaritons in an optical microcavity have already shown evidence of Bose-Einstein condensation (BEC) in the lowest quantum state in a harmonic trap. The theory of BEC and superfluidity of the microcavity excitonic polaritons in a harmonic potential trap is presented. Along the way, we determine a general method for defining the superfluid fraction in a two-dimensional trap, within the angular momentum representation. We discuss BEC of magnetoexcitonic polaritons (magnetopolaritons) in a QW and GL embedded in an optical microcavity in high magnetic field. It is shown that Rabi splitting in graphene is tunable by the external magnetic field B, while in a QW the Rabi splitting does not depend on the magnetic field in the strong B limit.
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Affiliation(s)
- Oleg L Berman
- Physics Department, New York City College of Technology, City University of New York, Brooklyn, NY 11201, USA.
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12
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Vörös Z, Snoke DW, Pfeiffer L, West K. Direct measurement of exciton-exciton interaction energy. PHYSICAL REVIEW LETTERS 2009; 103:016403. [PMID: 19659162 DOI: 10.1103/physrevlett.103.016403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Indexed: 05/28/2023]
Abstract
We report a direct measurement of the spectral function (real and imaginary self-energy) of excitons with a repulsive interaction potential. These results allow a stringent test of many-body theories of the exciton-exciton interaction which is independent of the exciton density calibration.
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Affiliation(s)
- Z Vörös
- Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, Pennsylvania 15260, USA
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13
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Sonin EB. Gauge-field rotation of an electrically polarized bose condensate by a radial magnetic field. PHYSICAL REVIEW LETTERS 2009; 102:106407. [PMID: 19392139 DOI: 10.1103/physrevlett.102.106407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Indexed: 05/27/2023]
Abstract
Here it is shown that a condensate of electrically polarized bosons subject to a radial magnetic field must rotate due to the Aharonov-Bohm effect. As in mechanically rotated superfluids, rotation is accompanied by penetration of vortices into the condensate at some critical magnetic field. In the case of a Bose-condensed exciton cloud in a double-quantum well, a necessary electric polarization is provided with spatial separation of electrons and holes forming excitons. Penetration of vortices strongly affects the intensity and the angular distribution of photoluminescence from the exciton cloud. This effect can be used for an experimental manifestation of exciton Bose condensation.
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Affiliation(s)
- E B Sonin
- Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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Yao W, Niu Q. Berry phase effect on the exciton transport and on the exciton Bose-Einstein condensate. PHYSICAL REVIEW LETTERS 2008; 101:106401. [PMID: 18851231 DOI: 10.1103/physrevlett.101.106401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2008] [Revised: 07/23/2008] [Indexed: 05/26/2023]
Abstract
With the exciton lifetime much extended in semiconductor quantum-well structures, the exciton transport and Bose-Einstein condensation have become a focus of research in recent years. We reveal a momentum-space gauge field in the exciton center-of-mass dynamics due to Berry phase effects. We predict a spin-dependent transport of the excitons analogous to the anomalous Hall and Nernst effects for electrons. We also predict spin-dependent circulation of a trapped exciton gas and instability in an exciton condensate in favor of vortex formation.
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Affiliation(s)
- Wang Yao
- Department of Physics, The University of Texas, Austin, Texas 78712, USA.
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Wouters M, Carusotto I. Excitations in a nonequilibrium Bose-Einstein condensate of exciton polaritons. PHYSICAL REVIEW LETTERS 2007; 99:140402. [PMID: 17930649 DOI: 10.1103/physrevlett.99.140402] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Indexed: 05/25/2023]
Abstract
We develop a mean-field theory of the dynamics of a nonequilibrium Bose-Einstein condensate of exciton polaritons in a semiconductor microcavity. The spectrum of elementary excitations around the stationary state is analytically studied by means of a generalized Gross-Pitaevskii equation. A diffusive behavior of the Goldstone mode is found in the spatially homogeneous case and new features are predicted for the Josephson effect in a two-well geometry.
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Affiliation(s)
- Michiel Wouters
- TFVS, Universiteit Antwerpen, Groenenborgerlaan 171, 2020, Antwerpen, Belgium
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Mouchliadis L, Ivanov AL. Anti-trapping of indirect excitons by a current filament. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295215. [PMID: 21483067 DOI: 10.1088/0953-8984/19/29/295215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In order to explain the photoluminescence (PL) of indirect excitons collected from localized spots in experiments with a defocused laser excitation of coupled quantum wells (QWs), we model the in-plane carrier transport and charge distribution with a set of drift-diffusion, Poisson and thermalization equations. The quantum statistical corrections are included in our description via a generalized Einstein relationship and quantum mass action law. The PL spots are attributed to transverse current filaments crossing the structure and injecting electrons in the coupled QWs. The accumulated electron charge forms an anti-trap for indirect excitons. Our model quantitatively reproduces the whole set of the relevant experimental data.
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Affiliation(s)
- L Mouchliadis
- Department of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK
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Vörös Z, Hartwell V, Snoke DW, Pfeiffer L, West K. Considerations on equilibration of two-dimensional excitons in coupled quantum well structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295216. [PMID: 21483068 DOI: 10.1088/0953-8984/19/29/295216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this paper we discuss the issues of the equilibration dynamics of spatially indirect two-dimensional excitons in a coupled quantum well structure, in particular those trapped by an in-plane harmonic potential trap. We discuss the relative timescales for several processes. In the experiments with an in-plane trap, we can use the size of the exciton cloud as a measure of the temperature of particles. At low lattice temperatures the exciton temperature is higher than that of the lattice, even long after equilibrium has obviously been reached. We discuss the effects that can be responsible for this.
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Affiliation(s)
- Z Vörös
- University of Pittsburgh, Pittsburgh, PA 15260, USA
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Butov LV. Cold exciton gases in coupled quantum well structures. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295202. [PMID: 21483054 DOI: 10.1088/0953-8984/19/29/295202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Cold exciton gases can be implemented in coupled quantum well structures. In this contribution, we review briefly the recent works on spontaneous coherence of cold excitons and on trapping of cold excitons with laser light.
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Affiliation(s)
- L V Butov
- Department of Physics, University of California at San Diego, La Jolla, CA 92093-0319, USA
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Savona V. Effect of interface disorder on quantum well excitons and microcavity polaritons. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:295208. [PMID: 21483060 DOI: 10.1088/0953-8984/19/29/295208] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The theory of the linear optical response of excitons in quantum wells and polaritons in planar semiconductor microcavities is reviewed, in the light of the existing experiments. For quantum well excitons, it is shown that disorder mainly affects the exciton centre-of-mass motion and is modelled by an effective Schrödinger equation in two dimensions. For polaritons, a unified model accounting for quantum well roughness and fluctuations of the microcavity thickness is developed. Numerical results confirm that polaritons are mostly affected by disorder acting on the photon component, thus confirming existing studies on the influence of exciton disorder. The polariton localization length is estimated to be in the few-micrometres range, depending on the amplitude of disorder, in agreement with recent experimental findings.
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Affiliation(s)
- Vincenzo Savona
- Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
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Balili R, Hartwell V, Snoke D, Pfeiffer L, West K. Bose-Einstein Condensation of Microcavity Polaritons in a Trap. Science 2007; 316:1007-10. [PMID: 17510360 DOI: 10.1126/science.1140990] [Citation(s) in RCA: 262] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We have created polaritons in a harmonic potential trap analogous to atoms in optical traps. The trap can be loaded by creating polaritons 50 micrometers from its center that are allowed to drift into the trap. When the density of polaritons exceeds a critical threshold, we observe a number of signatures of Bose-Einstein condensation: spectral and spatial narrowing, a peak at zero momentum in the momentum distribution, first-order coherence, and spontaneous linear polarization of the light emission. The polaritons, which are eigenstates of the light-matter system in a microcavity, remain in the strong coupling regime while going through this dynamical phase transition.
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Affiliation(s)
- R Balili
- Department of Physics and Astronomy, University of Pittsburgh, 3841 O'Hara Street, Pittsburgh, PA 15260, USA
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